Electric arc furnace



May 13, 1952 w. E. MOORE 2,596,708

7 ELECTRIC ARC FURNACE.

Filed May 17, 1947 2 SHEETS-SHEET 1 IN V EN TOR.

W/W/b/n E Moore P AUM HA5 ATTORNEYS May 13, 1952 w. E. MOORE ELECTRICARC FURNACE 2 SHEETSSHEET 2 Filed May 1'7, 1947 INVENTOR. W/Mam E./7002'@ H/S ATTORNEYS Patented May 13, 1952 ELECTRIC ARC FURNACE WilliamE. Moore, Pittsburgh, Pa., assignor to Delaware Engineering Corporation,Pittsburgh, Pa., a corporation of Delaware Application May 17, 1947,Serial No. 748,727

This invention relates in general to electric arc furnace andparticularly to electrode operating gear for automatically controllingthe movements of the electrodes of an electric arc furnace for thepurpose of maintaining the positions of the electrodes relative to thecharge so that the arc may be maintained at relatively constant lengthand the furnace operated eiliciently.

Variations in the arc or spark gap causes variations in the electricpower supply to the furnace, and my invention employs such powervariations to control the operation of fluid-actuated mechanism to movethe electrode toward or away from the furnace charge so that the are orgap may be kept as uniform as possible, thus contributing to thesatisfactory operation of the furnace.

There is provided a reversible electric motor which is instantlyresponsive to variations in the arc of the furnace, and which isdirectly connected to pump mechanism adapted to control the flow of aliquid under pressure from a reservoir to a hydraulic motor which isused to quickly regulate the movement of the electrode arm andassociated electrodes. The pump, when reversed, causes a prompt reversalof the liquid flow while the motor is instantly responsive to variationsin the electric current supplied to the electrode either in the amperageor voltage or to a combination of them, depending on thecurrent-responsive mechanism which is used to control the motoroperation. I prefer to counterbalance the weight of the electrode armand associated movable structure by the use of a fluid-operated motorconnected to a source of liquid preferably under a predeterminedpressure. This will enable the position of the electrode to be adjustedby a relatively small application of power applied to'the pressure fluidsince it is only necessary to exert sufficient pressure to overcome theinertia of the movable parts. The control which Iv contemplate is ofsuch a nature that when the electrode is positioned so as to provide thedetermined arc, the pump motor will be inactive. In the operation ofsystems of this character it is not unusual to find that air becomesentrapped in the hydraulic motor and causes a "jumpy action of theelectrode. I provide means whereby entrapped air is removed bythe actionof the pump when lowering the electrode.

My invention will be illustrated asapplied to one electrode of a wellknown electric arc furnace, but the arrangement is the same for eachelectrode whether there be two or more (usually three) employed,

4 Claims. (01. 314--61) The invention may be more fully understood byreference to the accompanying drawings in which I have shown forpurposes of illustration only certain more or less schematic views of anelectric furnace showing the presently preferred embodiment of myinvention. In the drawings:

Figure l is a diagrammatic elevation of one embodiment of my invention;

Figure 2 is a view chiefly in section, of the fluid motor which I use;and

Figure 3 is a view partly in section of a suitable valve which I mayemploy.

In the drawings the furnace 2 is of conventional design. A usual chargeof metal 3 is shown. A single electrode is illustrated at 4, but theremay be any desired number of such electrodes (usually three), but forpresent purposes it will be sufficient to describe the furnace as havingonly one electrode. The electrode 4 is made of carbon or graphite, andis supported by and electrically connectedto an electrode arm 5, whicharm is physically connected to, but insulated from the closed end orhead of the hydraulic power cylinder 6 in which there is a cooperatingplunger or ram 1. The ram 7 is held stationary relative to the furnace 2by suitable framework and moves with the furnace. The cylinder is guidedin rollers 8 which are secured to the side of the furnace, but which,for clearness of illustration, are only conventionally shown in Fig. 1.Movement of the cylinder 6 relative to the fixed piston 7 will cause theelectrode 4 to approach or withdraw from the metal charge 3. Thecylinder travels through adjustable rollers by 8 or other guides in adirection parallel to the longitudinal axis of the electrode 4 andram 1. Electric power from a line 9 is supplied to the electrode througha cable 10.

Connected to the bottom of the ram 1 and to a passage which extendsaxially therethrough is a supply pipe II which passes through awatercooled heat exchanger l2 and thence through pipe I3 an extension ofsupply pipe I I to one side of a reversible metering pump 14, which isof any usual or preferred construction, such as a gear type or eccentrictype. The opposite side of the pump 14 is connected to a feed pipe l5, avalve l6, and a feed pipe H, to a fluid pressure reservoir I8. The pipel5 has a branch pipe [9 which leads through a valve 20, and a dischargepipe 2| to a spray pipe 22 located close to the inside upper portion ofthe tank l8. By means of'this spray pipe, oil or other liquid may beforced against the upper inside surface of the tank and thus cooled. Themake-up liquid supplied to the tank !8 may be furnished by avalvecontrolled liquid supply pipe 23. A pressure relief valve 25, apressure indicating gauge 25, and a fluid level sight indicator isconnected to the tank It as illustrated. An automatically regulatedcompressor 2'! maintains a desired uniform pressure on the liquid 28inside the reservoir l8 of such a magnitude that when transmittedthrough the pump l4, even when it is not being driven, will more or lessbalance the electrode mounting assembly so that the pump has only tosupply the increased pressure needed to overcome the friction of the ramI. For most operating conditions, I prefer to have the cylinder 6 andassociated electrode assembly overbalanced by the fluid pressure so thatin case of failure of the pump it or its motor or the motor powersupply, the electrode assembly would be raised clear of the furnacecharge 3 and thus prevent the carbon electrode from dipping into thebath and causing damage by carbonization of the charge and wasting awaythe electrode.

The reversible pump i4 is driven by a reversible motor 39, the operationof which is controlled by a control unit 3|, electromagnetically orelectronically operated by variations in the current supplied theelectrode as indicated. Controls of this kind are well known in the artand are commercially available through suppliers, such as WestinghouseElectric and Manufacturing Company, General Electric Company,Allis-Chalmers Company, and others. The arrangement in general is suchas to cause the pump to force fluid into the hydraulic motor when thefurnace arc is too short, and to withdraw fluid when the arc is toolong.

To avoid excessive over-pressure from the pump being exerted against thecylinder 6, such as would be caused when the cylinder reaches the toplimit of its upward travel while the pump would still be running, Iprovide a relief pipe 32 connected at one end to the pipe 2| and at theother end to the pipe [3, and at a position between the pump i4 and thecooler l2. A pressure relief valve 33 opening toward pipe 2| is providedin relief pipe 32. Any pressure exerted by the pump M in the directionof the hydraulic motor, when the pressure reaches a predetermined value,deemed excessive, would cause the fluid to be by-passed through pipe 32,valve 33, and pipe 25 to tank !3. This condition may prevail when theelectrode is raised to the upper limit of its travel.

The pump i4 is provided with a customary spring-adjusted vacuum breakervalve 34 usually mounted on the pump housing. This vacuum breaker valvewill open and admit air to the pump and relieve its suction in case thepump should continue to operate after the lower limit of the stroke ofthe cylinder 6 has been reached. The pump will then fill with air tominimize the suction. Some of this air in turn might be dischargedthrough the pipes l3 and H into the cylinder 6. Not infrequently airalso will leak into cylinder 6. The presence of air in cylinder where itgathers at the top tends to cause a bouncing or jumping motion of thecylinder and connected gear. Accordingly, it is one of the features ofmy fluid motor arrangement to provide for the evacuation of air whichmay accumulate in the top of cylinder 6. This I do by causing the pipethrough which fluid passes to and from the cylinder 6 to terminateclosely adjacent the top of the cylinder. While I could connect pipe i idirectly to the top of cylinder 6,

I prefer not to expose pipe H to the intense heat of the furnace whichwould injuriously affect the oil. I prefer to provide (see Figure 2) apipe or supply tube 35 which is attached to the top head of the cylinder6 by means of a spider casing 36 which is perforated along the topportion. The pipe 35 is slidably received inside a pipe or passage 31connected to the lower end of the ram 1 and to the pipe by II. It isevident that liquid will be transmitted directly to and from the top ofthe cylinder 6 by this telescoping pipe arrangement. The pump M on thefirst return operation of lowering the cylinder 6 must first draw anyair that may be present from the top of the cylinder 6 and the liquidlevel will then rise sufliciently high to minimize the air cushion inthe top of the cylinder 6 to the point where there is no objectionablejumping motion. The pumped air will finally pass into the top of thetank I8.

The hydraulic motor is mounted adjacent the furnace wall and is subjectto considerable heat when the furnace is in operation. Motor-operatingliquid, usually a hydrocarbon oil, when sub jected to heat, tends todeteriorate, its fluidity is greatly increased, and there is a tendencyto foaming. It is quite difficult to keep a hydraulic system fluid tightwhen thin oil is used. To obviate the undesirable effects of furnaceheat on the oil, I provide a water jacket 38 for the cylinder,preferably for a distance generally equivalent to the piston travel.Cooling water may be supplied through a conveniently located inlet 39and discharged through the outlet 40.

In ordinary operation, oil is delivered to the pump |4 through pipe l1,check valve [6 (opening toward the pump) and is forced through pipe l3,cooler l2, pipe passage 31 and pipe 35 to the top of the cylinder 6 andcauses the cylinder and attached electrode gear to rise and lengthen thegap between the electrode 4 and the furnace charge 3. When the cylinder6 is being lowered, the pump |4 reverses, receives fluid from pipe 35,passage 31, pipe II, cooler l2 and pipe 13, and discharges it throughthe check valve 20 (which opens away from the pump), through the pipe 2spray pipe 22, into the top of tank l8.

Although valves l6 and 20 may be ordinary check valves, I prefer to usewhat I term a springrelief-check-stop valve arranged as shown in Figure3, so that by screwing up or down on the valve handle the valve may beset to operate as: (a) a spring-pressure-relief valve; (2)) a checkvalve; (0) or (when screwed down) as a stop valve. The valve consists ofa wall 4| which defines a chamber which is divided by a partition 42into two compartments 43 and 44. The wall has two openings 45 andleading into the compartments 43 and 44 respectively. The partition 42has a valve opening 41 which may be closed by the valve plug 46.Upstanding from the wall 4| and threaded to it is a tubular housing orbon net 49, the upper end of which is closed by a cap 50. The valve plughas a projecting guide portion 5| which is received in an axial opening52 of a movable valve plug guide 53 which has serrated sides and anupwardly-extending axial stem 54. The valve plug guide 53 is urgeddownwardly by a coiled spring 55 which at its lower end bears against ashoulder of the guide 53 and at its upper end bears against a springseat 56 which has an opening 51 through which the plug guide stem 54extends. Threadedly received at 58 in the inside of a valve stem bonnet59 is a valve stem 60 which passes through the cap 50 and at its lowerend may bear against the upper surface of the spring seat 56. The lowerportion of the valve stem 60 has an opening Si in which the upper end ofthe plug guide stem 54 may be received. The valve stem is rotated by avalve handle 62, attached to the upper end. Necessary packings to makethe joints fluid-tight are arranged at locations 63, 64 and 65.

If it is desired to use the valve as a stop valve, the valve stem 60 isturned so as to compress the spring 55 which will urge the valve plugagainst the seat of the valve opening. By subjecting the spring tosuflicient pressure, the valve plug may be tightly seated and willresist movement by any pressure exerted by the fiuid in compartment 43.If it is desired to use the valve as a pressure relief valve, the spring55 is compressed to the extent that the plug 41 will not rise until apredetermined pressure is attained in the compartment 43. When used as acheck valve to allow fluid to flow relatively freely from compartment 43to compartment 42 but to prevent reverse flow, the spring pressure willbe adjusted so as to allow the desired flow but will prevent itsreverseflow. It is to be understood that whereas I have described asuitable type of valve for use where valves 16 and are indicated, I mayuse an ordinary check valve at I6 and a pressure relief valve at 20, thelatter valve also serving to prevent reverse flow through it. Also it isto be understood that various valves, drain valves and relief valves,may be placed in the system where desired for maintenance or otherpurpose.

It is also possible to operate my system without fluid pressure in tankI8, in which case the apparatus will be operated without thecounterbalancing pressure normally supplied by the fluid in the tank. Insuch instance the valve I6 would be set as a check valve to admit fluidtoward the pump [4, and valve 2t would be set as a pressure relief valveso that the cylinder and electrode gear would not settle by gravity whenthe pump 14 is not being operated. The weight of the cylinder andelectrode gear would be sustained by means of the fluid pressure trappedin the cylinder and fluid connections by the valve 20. The valve 20would be set so that only the added pressure which might be exerted bythe pump l4 would cause it to open toward the tank 48. When the cylinderis to be lowered, the pump l4 would, in combination with the pressureexerted by the cylinder 6 and associated gear, provide sufficientpressure to open the valve and allow the fluid to flow to the tank [3.

Certain features of the apparatus disclosed in this application areshown in my copending application Serial No. 498,317, filed August 12,1943, now Patent #2,517,52'7, issued August 1, 1950, and in my copendingapplication Serial No. 760,031, filed July 10, 1947, now Patent#2,517,528, issued August 1, 1950, to which reference is made for a moredetailed showing of the common subject matter.

While I have described certain exemplary embodiments of my invention, itis to be understood that various changes may be made within the scope ofmy claims.

I claim:

1. In apparatus for elevating and lowering an electrode and supportingstructure therefor in an electric arc furnace, an hydraulic motorcomprising a stationary piston having its axis vertical and alongitudinally and vertically extending bore therein, a cylinder mountedon said piston and having a connection with the electrode supportingstructure for imparting'ra'ising and lowering movements to theelectrode, a pipe through which hydraulic liquid may be supplied to andexhausted from said cylinder, means mounting said pipe in said cylinderfor movement therewith and with its lower end telescoping in said boreand its upper end terminating adjacent the vertically upper end of saidcylinder, and means connected with said bore for controlling the flow ofliquid to and from said cylinder through said pipe, the termination ofthe upper end of said pipe adjacent the upper end of said cylinder beingeilective to release entrapped air and gas from said cylinder prior tothe exhaust of any liquid therefrom to thereby eliminate bouncingmovement of the electrode due to such entrapped air and gas.

2. In apparatus for elevating and lowering an electrode and supportingstructure therefor in an electric arc furnace, an hydraulic motorcomprising a stationary piston having its axis vertical and alongitudinally and vertically extending bore therein, a cylinder mountedon said piston and having a connection with the electrode supportingstructure for imparting raising and lowering movements to the electrode,a pipe through which hydraulic liquid may be supplied to and exhaustedfrom said cylinder, means mounting said pipe in said cylinder formovement therewith and with its lower end telescoping in said bore andits upper end terminating adjacent the vertically upper end of saidcylinder, means connected with said bore for controlling the flow ofliquid to and from said cylinder through said pipe, the termination ofthe upper end of said pipe adjacent the upper end of said cylinder beingeffective to release entrapped air and gas from said cylinder prior tothe exhaust of any liquid therefrom to thereby eliminate bouncingmovement of the electrode due to such entrapped air and gas, and meansresponsive to the electrical operating conditions of said electrode foroperating said control means.

3. In apparatus for elevating and lowering an electrode and supportingstructure therefor in an electric furnace, a vertically extendinghydraulic motor connected to the electrode and supporting structure forraising and lowering the same and comprising piston and cylinderelements cooperating to define a vertically extending and expansiblechamber therebetween, means for supplying and exhausting hydraulic fluidto and from said chamber comprising a tube connected to one of saidelements for movement therewith and having its upper end permanentlypositioned adjacent the upper end of said expansible chamber, the otherof said elements having an opening therein in which the lower end ofsaid tube is telescopically receivable, and means for supplyinghydraulic fluid to and exhausting it from said tube to control theoperation of said motor elements in effecting raising and loweringmovements of said electrode, the positioning of the upper end of saidtube being effective to remove entrapped air and gas from said chamberbefore the exhaust of any hydraulic fluid to thereby eliminate bouncingmovement of the electrode due to such entrapped air and gas.

4. In apparatus for elevating and lowering an electrode and supportingstructure therefor in an electric furnace, a vertically extendinghydraulic motor connected to the electrode and supporting structure forraising and lowering the same and comprising piston and cylinderelements cooperating to define a vertically extending and expansiblechamber therebetween, a part providing an inlet and exhaust portpermanently positioned adjacent the upper end of said chamber, said partbeing connected with one of said motor elements for movement therewith,and means operative through said port for supplying hydraulic fluid toand exhausting it from said chamber in effecting raising and loweringmovements of said electrode, the positioning of said port adjacent theupper end of said chamber being effective to remove entrapped air andgas from said chamber before the exhaust of any hydraulic fluid tothereby eliminate bouncing movement of the electrode due to suchentrapped air and gas.

WILLIAM E. MOORE.

REFERENCES CITED The following references are of record in the file ofthis patent:

Number 8 UNITED STATES PATENTS Name Date Johnson Dec. 31, 1918 HalsteadJan. 18, 1927 Seede Oct. 18, 1927 Tagliaferri Aug. 26, 1930 Emmert Mar.20, 1934 Glab June 5, 1934 Eklund May 21, 1940 Payne Sept. 22, 1942Hopkins Sept. 29, 1942 Henry July 11, 1944 Payne Nov. 20, 1945 MooreDec. 3, 1946 Payne Apr. 27, 1948

